CHAP. XI.] HANTONIAN PERIOD. 231 



sufficient to account for the difference between the faunas 

 of the Bracklesham and Barton Beds. 



Oligocene Time. At the commencement of the Oligocene 

 period the geography of Britain can hardly have differed 

 much from that of the later Eocene time. England, Scot- 

 land, and Ireland still formed one united mass of land, 

 which was joined to France across what is now the western 

 opening of the English Channel, so that the Atlantic had 

 no communication with the area of the German Ocean. 

 The waters of the latter extended south-eastward through 

 Holland and over part of Belgium, but did not cover the 

 south of Belgium nor the south-east of England. 



In the Anglo-French area the passage beds between the 

 Eocene and Oligocene show that the water in which they 

 were deposited became rapidly shallow, and the strong 

 unconformity between the two formations in Belgium 

 proves that this shallowing was mainly due to a general 

 upheaval of the whole of western Europe. 1 By this uplift 

 the sea spaces were contracted, and land connections were 

 formed with the African continent ; Europe was invaded 

 by a number of new terrestrial animals, and thus the 

 Oligocene is marked by the introduction of a new and 

 peculiar mammalian fauna, while the mollusca are obviously 

 the descendants of the species which inhabited the northern 

 province at the close of the Eocene period. 



Let us now endeavour to restore the geographical out- 

 lines of southern Britain at this period. We may conclude 

 that the western part of the country, including the land 

 which then lay to the south of Ireland and united Corn- 

 wall to Brittany, was a region of hills and mountains, 

 among which at least one large river had its origin. This 

 river emptied itself into an estuary which lay at the north- 



1 The principal upheaval of the Pyrenees is believed to have taken 

 place at this time. 



